The present invention relates to a conveyor system utilized to move wheeled trucks along a predetermined pathway. In particular, the trucks have a tow pin which can be lowered into engagement with a driver on the chain. The wheels of the trucks ride on a roadway on both sides of a track housing a chain and are guided to follow the track. The chain track turns corners in a building and the truck follows in alignment with the chain. On top of the truck is a turntable which can be rotated. Automatic turning mechanisms on the roadway are provided for rotating the turntable 90.degree. through coaction with a four-armed, cross-lever mounted through the truck and non-rotatably attached to the turntable. Two types of chain disengagement mechanisms are provided to raise the tow pin on the truck. One is a pivotal disengagement cam lever located on the roadway and the other is a trailing disengaging cam fork on another truck which automatically disengages the tow pin on the adjacent truck before a rear-end collision between the two trucks can take place.
A chain conveyor system for transporting items of manufacture between work stations in a building is shown in U.S. Pat. No. 4,702,174 to Tredwell, et al issued Oct. 27, 1987 and the DeBorgh U.S. Pat. Nos. 2,317,675 of Apr., 1943 and 2,640,607 of Jun., 1953 cited therein. The conveyor in the Tredwell, et al patent requires lifting of the work surface of the truck prior to its rotation. Additionally, a manual foot lever on the truck is utilized to disengage the chain drive. Also disengagement ramps are periodically located along the roadway to automatically disengage the trucks from the chain drive. Re-engagement occurs when a predetermined number of trucks abut each other at a way-station and a new truck tries to enter the way-station. The incoming truck, by contact with the truck ahead, starts a chain reaction that pushes the first truck out of the way-station to again be moved by the chain drive.
The aforementioned Tredwell, et al system is set up so that the trucks have to collide with one another and additionally that one truck cannot be released to be driven by the chain until the way-station is filled. Also the mechanism for turning the top loading surface of the trucks requires the lifting thereof and this rotation is caused by impacting the loading surface with a fixed unyielding turning bar. Additionally, there is no selective disengagement of the drive train from the truck. The disengaging cams are fixed on the roadway and disconnect the drive whenever the truck reaches a cam.
Also, there is nothing provided in Tredwell, et al to keep a truck from rear-ending the truck ahead of it that has been stopped by disconnection of its drive to the chain. Quite to the contrary, Tredwell requires a series of rear-enders at a way-station as the necessary requirement to push a truck out of the way-station so that it can again be engaged by the drive chain.
This invention is directed to improving the conveying system of the Tredwell, et al patent by avoiding the above disadvantages.
Accordingly, it is an object of this invention to provide a selectively actuable disconnect for uncoupling a truck from the chain at a particular point along the track when desired, while permitting the truck to remain connected to the drive at that particular point if that is the desire.
Another object of the invention is to provide an anti-rear-end collision control to automatically disengage a following truck from the chain drive in order to keep it from rear-ending a stopped truck ahead of it.
Another object of the invention is to provide a turning mechanism for the work surface of a truck which does not require lifting of the work surface before turning.
A still further object of the invention provides for a cushioned mechanism to rotate the work surface of the truck without jarring.
Another feature of the invention is the provision of special turning track sections to provide for a smooth movement of the truck about a curve in the track.
The above objects are obtained by providing the trucks with a tow pin hanging down from the truck and spring biased downward to rest in the path of a driver tang on the chain. Engagement of the tow pin with the tang causes the tang to act as a pusher to move the truck along the track. Here an upper portion of the drive pin engages in the truck to keep the front of the truck in alignment with the tang. A tail guide pin also engages the track, but is too short to engage the drive tang on the chain. The tail pin keeps the rear of the truck in alignment with the guide track. Caster wheels on the truck rest on a roadway on each side of the track to support the truck and allow it to be driven forward when the tow pin is engaged by the tang. The fact that the wheels are on casters allows the truck to follow curves in the track.
In order to avoid excessive wear and jamming of the chain, the inside curves of the track have vertically aligned rollers to engage the chain and keep it in alignment with the truck while at the same time reducing friction of the track and the chain at the corners.
In order to provide the selective disengagement of the trucks from the drive train at desired locations along the track, pivoted disengagement cam levers are provided along the track. Normally these cams are in a withdrawn position. When it is desired to disengage the truck from the chain drive, the disengagement cam lever at the desired disconnect location is energized. Energizing of the disengagement cam lever causes it to be raised. The tow pin on each truck has a lower circular cam surface which comes into contact with the disengagement cam lever when the disengagement cam lever is in its raised position. This contact causes the disengagement cam lever to engage the lower circular cam surface and lift the tow pin (in opposition to its downwardly biasing spring) to a point above the drive tang on the chain, whereupon the truck will cease to be driven by the chain. When it is again desired to drive the truck by the chain, the disengagement cam lever is released and drops to its withdrawn position. The bias spring then forces the tow pin downward so that the tang on the chain can then engage the tow pin to push the truck along the track.
The invention also contemplates utilizing an automatic anti-rear-end collision control to disconnect the drive of a following truck should it get too close to the truck ahead of it. To this end, each truck has a disengagement camming fork at its rear-end. The tow pin on each truck also has a second and upper circular cam surface on it. This second cam surface will engage the rearwardly extending camming fork of the truck ahead of it, should the trucks get too close (approximately within two inches of one another, but any separating distance can be selected). Engagement of a rearwardly extending camming fork with the second camming surface causes the tow pin to be raised in a similar fashion as when the first camming surface thereon is engaging the pivoting disengagement cam lever. The cam fork will thus raise the tow pin to a point where it no longer is engaged by the driving tang on the chain and hence the drive to the truck (second in line) will be disconnected so that it will not rear-end the truck ahead of it. Thus, the invention allows for the stopping of one truck by the pivoting of a disengagement cam lever and insures following trucks will not rear-end it.
As the truck negotiates a turn, or even on straight-away track sections, it is sometimes desirable to reorient goods on the truck 90.degree.. This could occur for a painting operation, an assembly operation, etc. To this end, each truck is equipped with a turntable top. This top has a rotator spindle shaft fixedly connected to its center. The rotator shaft extends downward through an opening in the truck so as to be rotatable with respect to the truck. At a bottom end of the shaft are a first set of two arms, extending in a straight line and oriented at 180.degree. from one another. Above this set of arms is an additional set of two arms, extending in a straight line and oriented at 180.degree. from one another and at 90.degree. from the first set of arms. Turntable turning assemblies are located adjacent points along the track where rotation is desired. The turntable turning assemblies have a cam surface in line with one of the two sets of arms and can engage one of the arms that extends at right angles to the path of travel of the truck. When an arm engages the cam surface it is restrained from movement. As the truck proceeds down the track the turntable turning assembly causes the restrained arm to pivot about its axis 90.degree., thus rotating the turntable 90.degree.. On the top side of the truck and facing the turntable there is a spring biased detent that engages in one of four detent holes, spaced 90.degree. around the underside of the turntable. This detent holds the turntable in one of four angular positions with respect to the truck.
By having two sets of arms and turntable turning assemblies at two different heights, the turntable turning assemblies can be closer together along the track, since the upper set of spindle paddle arms can pass over the lower turning cam surface. Thus 180.degree. rotation can occur in a short distance along the track.
Likewise, by having the two cam surfaces of the tow pin at different heights, either one can be actuated independently of the other and jamming between a trailing disengaging cam fork or pivoting disengaging cam lever cannot occur.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.